This graphic shows a simulation of a barotropic instability on a rotating, doubly periodic plane over 30 days, computed with the HPM method. Shown are: the potential vorticity contours (top left), the particle velocity field (top right), the geopotential height (bottom left), and diagonostics such as total energy and divergence level (bottom right). This avi-file (8MB) includes a lower resolution simulation for 15 days. Diagonostics are total energy(blue), potential(green) and kinetic(red) energies and the ageostrophic kinetic energy(cyan), an adiabatic invariant (lower right).